Refrigerated dryers are in wide use in industry to treat compressed gases such as air. Compressed air dryers reduce the quantity of water vapor, liquid water, hydrocarbon, and hydrocarbon vapor in compressed air because moisture in compressed air is harmful. Water damages a compressed air system in several ways: erosion, corrosion, microbial contamination and freezing. Erosion is caused by water mist eroding piping, valves and other system components. Corrosion is caused by mist when it condenses and combines with salts and acids within the system to form highly corrosive solutions. Microbial contamination is caused when moisture supplies a growth medium for bacteria and mold, which produce acidic waste and can be a health threat, especially in food related applications. Finally, when water freezes in compressed air lines, this can lead to shutting down of the entire system, which results in tremendous loss of productivity. Drying wet compressed air minimizes these harmful effects.
Compressed air is dried to protect the system's piping and process equipment. Dry air also protects against lost product. Most pneumatic equipment have a recommended operating pressure, dryness level, and a maximum operating temperature.
Refrigerated air dryers utilize a mechanical refrigeration system to cool the compressed air and condense water and hydrocarbon vapor. Most refrigerated air dryers cool the compressed air to a temperature of approximately 35 degrees to 50 degrees Fahrenheit which results in a pressure dew point range of 33 degrees to 39 degrees Fahrenheit. This range permits the pressure dew point to fall within limits that are achievable with common refrigeration system controls. Refrigerated air dryers are available in two basic configurations, non-cycling and cycling.
There are many uses for compressed air that require a reduction in the vaporous contaminants as well as the elimination of all liquids. Typical conventional refrigerated air dryers pass the compressed air through a refrigerant-to-compressed air heat exchanger where the compressed air is cooled, condensing condensable material contained in the air stream. A separator then removes the condensate and the compressed air continues on to its end application. The unit of measure for capacity related to a refrigerated dryer is standard cubic feet per minute, (SCFM) referenced to a specific pressure, temperature and relative humidity. Typically, SCFM is referenced to 14.7 PSIA, 68 degrees Fahrenheit and 0% relative humidity.
Conventionally, the engineer selects from a variety of heat exchangers, condensing units, separators and other components to determine which configuration is best for a particular capacity refrigerated dryer. This is disadvantageous in that there is greater lead time due to the engineering involved in designing each refrigerated dryer per its particular requirement. Also, each of the components must then be specifically manufactured, which leads to increased cost.
While the foregoing systems are useful, improvements are still desirable. For example, the existing systems may require a great deal of engineering. For each type of need or size requirement, research may need to be conducted to determine which capacity of refrigerated dryer is required and what type of components are required to fulfill that need. Moreover, the various components need to be manufactured, which sometimes takes a considerable amount of time.
It is therefore desirable to have the ability to service the user efficiently, meeting the user's needs in a timely, yet cost effective manner. It is beneficial that when large usage needs are present, a great deal of time need not be spent on designing a specially sized refrigerated dryer to fit the needs of that customer. Accordingly, it is desirable to provide a method and apparatus that increases capacity of refrigerated dryers in a highly efficient manner.